FIELD OF THE INVENTION
This invention relates to a process for producing a transparent electroconductive film on the surface of a substrate of, for example, glass, ceramics, etc., and more particularly to a process for producing a transparent electroconductive film of lower resistance with a smaller content of remaining organic components and less pinholes than those of the conventional transparent electroconductive film, which comprises applying a coating solution selected from (a) a coating solution comprising an inorganic indium compound free from a photosensitive group in the molecule or an inorganic tin compound free from a photosensitive group in the molecule, an organic ligand capable of complexing with metal such as indium or tin, and an organic solvent, (b) a coating solution comprising an organic indium compound free from a photosensitive group in the molecule, or an organic tin compound free from a photosensitive group in the molecule, and an organic solvent, and (c) the coating solution (a) or (b) further containing a dopant source or precursor to the surface of a substrate, thereby forming a film thereon, irradiating the substrate with irradiation capable of exciting organic groups, for example, ultraviolet rays in a state where the substrate is kept at a high temperature (100.degree.-600.degree. C.), and then baking the substrate at a high temperature.
Electrodes having a light transparency are used in display element such as liquid crystal display elements, plasma display elements, electroluminescence display elements, etc., photosensitive display elements such as photocells, solar battery, etc., anti-dew glass, etc.
Heretofore, (1) vacuum vapor deposition process, (2) a sputtering process, (3) a CVD process, (4) a hot spray process, (5) a coating process, etc. have been known for producing a transparent electroconductive film. According to the processes (1) and (2), a film of lower resistance with good transparency can be produced, but the apparatus is expensive and is hard to apply to a substrate with a large area. The processes are also batch-wise and thus are not suitable for mass production. The processes (3) and (4) have such a disadvantage that a transparent electroconductive film with a uniform film quality is hard to produce on a substrate with a large area. On the other hand, the process (5) can produce a transparent electroconductive film uniformly on a substrate with a large area.
Typical of the coating process (5) are a process (a) of heat-setting a film of heat-setting type, followed by baking, and a process (b) of setting a film of ultraviolet setting type by means of ultraviolet rays, followed by baking. However, the resistance of transparent electroconductive films obtained according to these processes (a) and (b) is 500 .OMEGA./.quadrature. at the lowest for a film thickness of 1,000 A.